https://developer.valvesoftware.com/wiki/Steam_browser_protocol

This browser protocol makes steam do things. Type them in your browser or even in a windows shortcut to make steam do ♥♥♥♥. You can join servers, open the friends list, check your system hardware...

steam://friends/add/76561198128793141
steam://connect/162.248.92.106:27015
steam://exitSteam

Note that these very rarely will actually hyperlink, on pretty much any site. Sites often use them for quick links to join their gameservers.[intoxgaming.com]
Nor will they work if you use steam's markdown to put them in a post.

Steam has its automated 'spam filters' on posts, and of course is notorious for filtering swears and google drive links (but for some reason not mega.nz links anymore..), but there is also a frightening and bizarre filter in chat windows, that seems to be directed at mediafire and mediafire alone. I'd list more links if I could find any but I just can't. I tried some seriously nasty links but they're all fine except for mediafire.














They even make the highlighter in red...

While workshop collections were being developed it looks like they left in these testing options for the steam client, app id 7.
As it is now @ https://steamhost.cn/steamcommunity_com/workshop/editcollection/?appid=7:






It's reminiscent of these texts from tf2 leaks:

Swears are still filtered on forums in spite of turning filtering off
Try this guide.
https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=2250752160

https://steamhost.cn/steamcommunity_com/my/namehistory
https://steamhost.cn/steamcommunity_com/my/posthistory

Also, apparently these mascots that you'll see in older instruction pages or guides have names.[gaming.stackexchange.com]